Moon dogs (also called a mock moon or lunar halo) are a natural light phenomena that occur when moonlight is refracted by ice crystals in the air, creating a halo effect or light spots on the sides of the moon. Scientifically, they are known as paraselene or paraselenae (plural), and are quite a rare phenomena to see as they can only occur when the moon is full or nearly full. With the amount of ice crystals in the air on some Lapland winter evenings, they can occasionally be seen when there is a full moon and no cloud cover above (and of course ice crystals are present). They are very similar to sun dogs, however they do not show as much rainbow-like color.

Moon dogs occur in other places around the world so are not distinct to Lapland, but they are an extra special natural phenomena to observe when visiting, in addition to viewing the northern lights, midnight sun, polar night (kaamos), sun dogs, or autumn colors of ruska.